I've been slowly bringing a 1998 Legacy Outback back to life. Replaced full exhaust and cat. Installed downstream oxygen sensor thinking it was the only one needed. Threw code, did more research, learned about upstream sensor, installed. Car ran and drove although a little rough with just the downstream O2 sensor. Car refuses to start with upstream installed, even unplugged the harness, no change. Just pops and sputters. Have good fuel pressure. No codes when checked with scan tool. Going to try ECU reset when I get home tomorrow. Any thoughts as to where to go next. It's just odd as I drove the car about three weeks ago.

check all the hoses and clamps on the intake tube.

The O2 sensors are not the cause, they don't do anything until the engine reaches normal operating temperature. Then just fine tune the mix for low emmisions.

 

Check the CTS. Those can cause all kinds of weird and random running and starting problems, without causing a code. The FSM should have a simple ohmmeter test.

Thanks will check coolant temp sensor.

Edited June 9, 20178 yr by smokeeater495

check all the hoses and clamps on the intake tube.

 

+1

 

likely disconnected a PCV or the IAC hose. 

The CTS was broken, connector separated from the brass base. Thinking the engine is flooded now. Going to pull the plugs and see.

holding the gas pedal to the floor while cranking is the 'clear flood' mode.

+1 lucky texan. It may take a lot of cranking, but that should do it.

Check your oil to see if "flooding" has resulted in gasoline mixed with the oil. If you see the oil level is higher then normal, then change the oil pronto, as gasoline is now mixed with the oil. That combination results in very poor lubrication from the diluted oil.

Update. Still won't start. New plugs, old ones were mildly carboned. Changed oil, slight smell of gas. Cranks over, tries to fire when pedal is pushed to floor. Blue cloud from exhaust, smells like gas. So she was flooded. Still wont start. Pulled timing belt covers, all looks good inside. Timing marks look correct.

If new plugs, it should fire. Can pull them again, and hold a lighter to the tip briefly or use a propane torch to speed up being dry. If it wasn't a boxer engine, I'd say hold the torch over the exposed plug hole as that'll burn out any residue (works great on lawnmower engines tho you have to be careful. Maybe pull fuel pump fuse and crank engine several times in 5 sec. intervals (w/o any of the plugs in) to get some air in there if it was flooded that badly.

 

If it still won't start after drying them verify plug wires are connected in the correct order, verify it's still getting spark, and gas. Figure out which one it isn't getting and go from there.

Actually, I'd disconnect the downstream O2 1st and see if it fires. IF it's shorting internally, that can prevent engines from starting, and cause all sorts of issues. Had it happen in a Saab 9-3 where the heater element in the O2 was shorting, and caused severe backfires, stalls, etc. If the O2 is wrong or faulty, it might cause the same/similar issues.

Edited June 25, 20178 yr by Bushwick

absolutely NO CHANCE timing is off 2-3 teeth?

 

also, check that the IACV hose is connected under the intake tubing.

Update. Still won't start. New plugs, old ones were mildly carboned. Changed oil, slight smell of gas. Cranks over, tries to fire when pedal is pushed to floor. Blue cloud from exhaust, smells like gas. So she was flooded. Still wont start. Pulled timing belt covers, all looks good inside. Timing marks look correct.

 

 

Remember, you want to look at the "hash" or "line" markings on the edge of the pulleys, not the arrows in the middle.  Gotta check that even if the Cams are lining up with eachother, are they both lining up with the crank pulley.  So if you haven't pulled the center cover to check it would be worth it.

 

Without pulling the cover first, The quick and dirty way to check is to look at the 4 holes in the crank Dampener.  If they are not in a perfect straight up and down cross when the Cam hashes are up then its a few teeth off.

 

absolutely NO CHANCE timing is off 2-3 teeth?

 

also, check that the IACV hose is connected under the intake tubing.

 

 you want dashes up, not arrows.

 

 

And yes for sure double check the 3 pcv hoses and the IAC hose and the little vac line to the FP regulator and MAP sensor if equiped

Went to unplug the downstream 02 sensor and found it very loose in the bung, not sure how that happened as I installed it recently. Still no start. We tried ether and it acted like it was going to try to fire, still didn't. Pulled line off fuel filter, pressure good. So to recap. New fuel pump after no start problem, new CTS, new fuel filter, new plugs and has spark. All vacuum lines look correct. The car was running before. Frustrated.

The few times I had to clear a flood, it took *several* tries once it started to sputter / almost try to run, before it really caught.  With the pedal down the whole time.  Only let up once you get to a few 1000 RPMs.

Humor me here, but remove the gas cap, then see if it'll start (might take a bunch of cranking intervals). I've encountered problems where a bad cap wasn't allowing air in. Car was a 96' Lincoln Mark VIII. Would run fine, park it, and 5 minutes later would crank and crank. Car only had 70-80k miles at the time. Forget why what immediately made think "gas cap" back then, but I loosened it and it'd fire right up. Happened 3 times before I replaced it. Sold the car with 130k miles and it never happened again.

 

Also, fwiw, my Legacy had a leak in the fuel return line, under the rear seat area. As a temp fix as it was a winter failure, I pinched the return line under the hood with vice grips, to stop the leak. Car ran "fine", but like the Lincoln, it developed a no-start scenario after sitting (engine off) even as short as a 5 minute stop. Unpinched line, cranked until fired, then pinched line again to drive.

Edited June 27, 20178 yr by Bushwick

If all that changed was you messed with the exhaust and O2 sensor, it should run.  You should be able to run the car without any O2 sensors at all.

 

I'm still gonna bet you've got the air intake not installed correctly.  Loose hose?  Did you plug the MAF back in?